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Design of an overhead crane for the ITER NB cell remote handling maintenance operations
Fusion Engineering and Design 84 (2009) 1827–1832
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Design of an overhead crane for the ITER NB cell remote handling maintenance operations Gonzalo Taubmann a , Laurent Brochet a , Macarena Liniers b,∗ , Mercedes Medrano b , Xabier Sarasola b , Jose Botija b , Javier Alonso b , Carlo Damiani c a b c
IBERTEF A.I.E., Ibérica de Tecnología de Fusión, C/Magallanes 3, 28015 Madrid, Spain Asociación EURATOM-CIEMAT para la Fusión, Av. Complutense 22, 28040 Madrid, Spain FUSION FOR ENERGY, Josep Pla 2, Torres Diagonal Litoral Ed B3, 08019 Barcelona, Spain
a r t i c l e
i n f o
Article history: Available online 17 January 2009 Keywords: Neutral beam heating ITER Neutral beam cell Remote handling Monorail crane
a b s t r a c t In the neutral beam cell of ITER all the maintenance operations on the neutral beam components (BLC’s) must be performed by an overhead crane of large payload capability (30–50 tonnes). A crane system is presented consisting of a monorail, a carriage, and a lifting mechanism. The monorail must give access to the BLC’s in the beam line vessel, the front components connecting the NB vessel with the Tokamak, and a storage area at the north end of the NB cell. Rail switching points are required at the intersections between radial and toroidal branches. A translational switching mechanism is proposed. The crane carriage consists of two independent sub-carriages, each composed of four wheels. A set of four secondary wheels attached to the main carriage prevents the crane tilting due to the CoG misalignment of some loads. The elevation system proposed consists of an electromechanical crane of four independent drums and 50 tonnes payload. In parallel with the crane design, a logistics and space availability study has been carried out, leading to the detection of clearance or transport problems that could be taken into account in the final crane design. © 2008 Elsevier B.V. All rights reserved.
1. Introduction The neutral beam cell of ITER will house the three heating and current drive neutral beamlines (H&CD NB), and the diagnostic neutral beam (DNB). The estimated radiation level in the NB cell after 1000 h of Tokamak operation is enough to preclude manned interventions exceeding 30 min duration (Ref. [1]). Therefore provision is being made so that all the maintenance operations inside the NB cell can be performed by remote handling means. Logistics and space availability arguments have led to adopt the top maintenance scenario for the beam line components (BLC’s) and front components (FC’s) of the neutral beams (Ref. [2]), therefore the operations involved in the removal and reinstallation of any component shall be performed to a large extent by means of an overhead crane. The removed components will be transported with the crane to the hot cell entrance, in the east wall of the NB cell. The structural layout of the NB cell dictates the use of a monorail system: at the Tokamak side, the bioshield and front columns limit the horizontal clearance, whereas the available space above the beam line vessel is restricted by the NB cell pillars and the ion source bushing. Fig. 1 shows a schematic representation of the NB
∗ Corresponding author. Tel.: +34 91 346 0844; fax: +34 91 346 6124. E-mail address: [email protected] (M. Liniers). 0920-3796/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2008.11.058
cell with the monorail layout: the four radial branches on top of each injector will be used for the BLC’s maintenance, the toroidal branch has been laid down to optimize the service to the front components and the Tokamak upper port plugs. At the back of the injectors, along the NB cell north wall a temporary storage area has been foreseen, to accommodate some large size components that need to be removed in order to access the NB vessel top lid. Among those components are the top coils #4 and #5, and the passive shield plates, both belonging to the magnetic field reduction system (MFRS) (Ref. [3]). Rail switches are needed to connect the radial and toroidal branches during transport. A translational mechanism is proposed, after some detailed analysis of two alternative options. The advantages of the chosen mechanism are discussed in Section 2. The final layout of the monorail system is a result of the space availability study performed using the CAD models of the neutral beam cell and the present design of the BLC and FC components (Ref. [4]). In the final analysis the crane design has been included. The limits to the components dimensions set by the transport process have been established in this way, as well as the main crane requirements, such as payload and load maneuverability. The crane and rail have been designed for a payload of 50 tonnes. Although the weight of the components to be handled is under 30 tonnes, the crane must be dimensioned to manage large off center loads to ensure maneuverability of components at the front side, where
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Fig. 2. Front view of the rail and carriage. The auxiliary wheels are also shown.
Fig. 1. Top view of the NB cell from a CAD 3D model. The three H&CD injectors and the DNB injector are shown. The area near the north wall is used as temporary storage area.
a single toroidal rail must reach the NB front components and the upper port plugs. A further reason to adopt a high-payload crane is to leave open the possibility of transporting some heavy equipment needed for the ion source maintenance at the back area of the cell. The “maintenance corridors” defined by the removal and transport of all the components shall be respected, the laydown of the auxiliary systems such as cable trays, water cooling and cryolines, will be designed in accordance with this condition. Section 4 summarizes the main results of the space availability analysis. The crane itself has been the object of a thorough study. The carriage and elevation system are described in Section 3. Two different elevation systems have been put forward: an electromechanical system and a hydraulic one. The chosen option is the electromechanical crane, the hydraulic option has been discarded on safety grounds, the use of pressurized water in the NB cell is avoided to minimize the risk of water leaks. 2. The monorail and rail switches The crane has been designed for a payload of 50 tonnes if the CoG of the load is aligned with the crane vertical axis. A large payload of 50 tonnes is best managed by using a 4-rope lifting mechanism, which ensures load stability in the case of off-centred loads. If the CoG is not inside the crane “footprint” the extraction would produce a fast rotation and lateral displacement of the load right after the component is disengaged. As this is not acceptable, the layout of the rails and the lateral dimensions of the crane have been designed so that the centres of gravity of all the components are below the footprint of the crane at the moment of extraction. Fig. 2 shows a front view of the rail and a crane with a 2 m distance between ropes. The rail has similar shape than a standard HEB 500 profile, except that the lower wing is 60 mm (instead of 28 mm in the HEB 500) to avoid local bending. The deflection of the rail has been calculated as a function of the distance between supports to the ceiling. In the conservative assumption of a concentrated load, the deflection is below 1 mm for distances between supports up to 3 m. The width of the rail is 300 mm (±150 mm) so the maximum possible distance between wheels in transverse direction is approximately 260 mm. If the CoG of the equipment is misaligned with the rail vertical axis by more than 130 mm, the crane will rotate and the
equipment will have a lateral movement. To avoid this effect two lateral sets of reaction wheels are provided at each side of the crane. In case of off-centred loads, the crane will try to rotate and a reaction force is developed on the stability wheels. In this scenario, the load developed on the main wheels is larger than the weight of the equipment. If a shift between the load CoG and the crane axis exists, the load capability of the crane is diminished. For a given payload, the lateral dimensions of the crane define the maximum weight that can be extracted as a function of the misalignment between the CoG of the load and the rail vertical axis. In Fig. 3 there are plots of the maximum weight and the loads on the main and secondary wheels for a payload of 50 tonnes and a distance between ropes of 2 m. At the intersections between the radial and toroidal branches of the monorail, rail-switching devices are needed. Three different alternatives have been examined: the rotational switch, the translational switch and the toroidal rail. They are schematically represented in Fig. 4. Fig. 4a shows a layout of the rotational switch option. In order to cover all the required areas four switches are needed. During operation of the switching mechanism, the crane carriage hangs from the device, the rotating mechanism must cope with the full load of the crane. When the carriage is inside the rail-switch, a mechanical hard stop must be activated to ensure that the carriage will not move. A further difficulty of this kind of device is that a curtain type umbilical cannot be used. Therefore, friction contacts must be used for electric power and signals. For hydraulics, local connections could be used if required. The mechanical motion is achieved by rotating an external crown with respect to an internal, fixed crown. The movement is driven by an electric motor located in the upper level, engaged to the bearing crown through a pinion.
Fig. 3. Plot of the maximum load and loads on the main and secondary wheels as a function of CoG misalignment.
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upper level and connected to the device trough a rack and pinion. The translational switches are compatible with the use of a curtain type umbilical. Fig. 4c shows the general layout of the rail system in the NB cell when a toroidal rail is used near the Tokamak. The toroidal concept requires two carriages: the crane carriage, similar to that used in the previous options, and the toroidal mover carriage that performs the toroidal movement carrying the crane carriage along. The toroidal mover carriage has the ability to move toroidally and stop right in front of a radial rail. In this position, the crane carriage can move along the radial rail. The toroidal mover carriage has the maximum length allowed by the columns of the building. The area covered by the crane is increased significantly as compared with the other switching systems. The toroidal movement requires wheels to displace and support the carriage from the toroidal fixed rails. Four lines of wheels will perform this duty. The motorization of the toroidal movement is installed over the toroidal mover carriage and will consist of a pinion-rack system. Two racks are fixed on the ceiling at both sides of the toroidal mover carriage, and two independent drivers composed of a DC motor, a gearbox and a pinion will be fixed on the carriage and engage with the ceiling racks. The toroidal mover system allows the use of a curtain type umbilical. Of the three switching systems, the translational switch is recommended for its reliability and simplicity. The main advantages are that the rail switch operations are performed under no load conditions, and that it requires a minimum number of switch manoeuvres for a given maintenance action, thereby reducing the risk of failure. 3. The crane: carriage and lifting mechanism
Fig. 4. Layout of the monorail with (a) rotational rail switches, (b) translational rail switches, (c) toroidal rail system.
Fig. 4b displays the monorail layout with translational rail switches. As in the rotational case, four switches are needed to cover the maintenance corridors in the NB cell. The translational switch is conceptually similar to the typical train rail-switch: a sector of rail coincident with the intersection between two directions is substituted with a mobile sector containing the two rails corresponding to both directions. The distance between rails is enough to allow the movement of the carriage without interference with the inactivated rail. The movement of the rail-switch, as opposed to the rotating device, is performed before the carriage hangs from the device, therefore under no load from the crane. Once the rail change is made the carriage can travel across the device, and no further operation of the switch is necessary for the return trip of the crane. Therefore, a given maintenance operation will require a lesser number of switch operations. The displacement of the switch is achieved by means of auxiliary transversal rails fixed to the ceiling. The mobile rails are supported from the transversal rails, therefore their height must be decreased. The loss in stiffness can be compensated using a more robust profile. The driving system consists of a motor located in the
The crane carriage moves along the rail and supports the elevation drivers. The crane dimensions brought over by stability criteria are so large that a monolithic carriage would result in a very large curvature radius. To minimize the curvature radius a solution with two small independent sub-carriages has been selected. As seen in Fig. 5a each sub-carriage is composed of four wheels, a U-shape structure and a free rotation rod to hold the elevation structure. The rod is supported through an axial effect bearing (SKF AXK 130170). Fig. 5b shows the complete carriage assembly with the two subcarriages and the elevation structure attached. Also in the figure are the four stability wheels needed to balance the torque exerted by an off-centre load. The stability wheels are directly attached to the main structure and run on two auxiliary rails parallel to the main rail. In the design of the elevation system the following criteria have been taken into account: - Vertical size. In the NB cell the vertical clearance between the ceiling and the highest material point along the crane way is 4580 mm. Within this distance must be accomodated the complete crane (rail + carriage + elevation system + grabbing frame) and the NB component to be handled, whose height can be as large as 2800 mm (calorimeter). Therefore, there is strong interest in making the vertical dimension of the crane as small as possible. - Number of ropes. The elevation system needs to handle large loads with great accuracy and stability. A 4-rope solution has therefore been chosen. - Independent movement of the ropes. It allows rotation of the load around two axes: the rail axis, and a transverse horizontal axis. This operational flexibility is needed to increase the transportability of large components by reducing their footprint, and to attain the required accuracy at component installation. Moreover the size of the gears or pistons is reduced with four independent ropes, thereby gaining in vertical clearance.
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Table 1 Comparison between electromechanical and hydraulic cranes. Construction case
Units
Commer.
Electromechanical
Maximum load Equipment rotation Height Length Width
tonne
25.4 X and Y 1444 3626 1500
30 X 1309 1800 2000
mm mm mm
Hydraulic
X and Y 1261 1800 2000
50 X 1459 3100 2060
X and Y 1285 3450 2060
30 X and Y 1239 4180 2428
50 X and Y 1319 4180 2428
Height represents the vertical distance between the roof and the lower level of the frame.
- Load capacity per rope. Ropes will have to withstand different loads depending on the position of the CoG. In the limit, if the CoG is precisely under a rope this rope will withstand the full load and the others will have no load. - Rope position control. Each rope has an independent position sensor to measure the vertical position of the frame. This system is independent of the elongation of the rope, so differential deformation can be compensated by the elevation system. Three different elevation systems have been studied, all of them fulfilling these criteria: 1. A commercial 30 tonnes).
electromechanical
crane
(maximum
load
Fig. 5. (a) Drawing of one of the two sub-carriages. (b) The two sub-carriages, the stability wheels and elevation system structure.
2. A four piston hydraulic crane (30 or 50 tonnes). 3. A custom made electromechanical crane (30 or 50 tonnes). Only the third crane will be described here, the comparison between the three options is summarized in Table 1. Fig. 6 presents a view of a CAD model of the 50 tonnes electromechanical crane. There are four drivers each composed of an electric motor and two gears. Each driver acts on a drum that elevates one rope. A parallel architecture drum-motor has been chosen in order to reduce the length of the crane. The reliability of the system is increased by including two redundant motors for each drum. An axial displacement will be provided to the drums so the rope keeps a constant position during elevation of the component. In the figure is shown the grappling frame with the latches that will grab and hold the component. Not shown are the security latches that attach the frame to the carriage so that transportation of the component is carried out in a safe way. Table 1 summarizes the dimensional and operational properties of the three cranes. The commercial version is only available for a maximum load of 30 tonnes therefore it must be ruled out if a payload of 50 tonnes is required. But it is shown here as a reference. The operational capabilities (rotation around X and Y axes) and the position accuracy of the electromechanical and hydraulic cranes are the same, the vertical dimension is similar in both cases, while the transverse dimensions of the hydraulic crane are larger. As shown in the table, four independent ropes (X and Y rotation) are advantageous over two sets of ropes on account of the vertical dimension, since the size of the gears/pistons is reduced. The payload choice has also an influence on the vertical dimension, but the gain achieved by reducing the payload from 50 to 30 tonnes (20 mm for the electromechanical or 80 mm for the hydraulic crane) does not justify the loss of manoeuvrability of large, off-centre loads. The hydraulic system requires an umbilical and the use of high-pressure (25 MPa) water tubes. This has been considered a drawback of the hydraulic option since there is a risk of a water leak in the NB cell. Taking into account all these considerations, the electromechanical crane of 50 tonnes and four independent ropes is the preferred option.
Fig. 6. View of the electromechanical crane with the grabbing frame.
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4. Space availability The space availability study concerns the neutral beam components whose maintenance is to be performed by the crane, and those that need to be removed in order to get access to them. These components are listed below: - Inside the NB vessel. Neutralizer, ion dump and calorimeter. - To get access to the NB vessel top lid, the following components must be removed. Active compensation coils (ACCC’s) #4 and #5, the passive shield (PS) plates. - The front components (FC’s). Shutter, absolute valve and duct bellows. - To get access to the FC’s. The balcony plates. The operations to be performed by the crane are essentially the removal of the component, its transport to the hot cell door, and the reverse operations of transport from the hot cell door and reinstallation of the component. Transport of the ACCC’s and PS plates to the temporary storage area must also be analysed. The main constraints to the space availability are: - The NB cell structure: the ceiling, horizontal beams, columns. - The layout of the H&CD NB’s and DNB, in particular the NB source bushings. - The layout of the vacuum vessel pressure suppression system (VVPSS). - The monorail layout and the crane. The space availability study depends on the monorail layout and the crane design that were proceeding in parallel. Therefore the study has advanced in an iterative way: starting with a monorail layout and preliminary crane design, the problems encountered were taken as input for a new design. Whenever the encountered clash could not be solved with a proper crane design, a proposal was made to modify the component or structural element of the NB cell. Some of the modifications to the NB cell that have resulted from this study are: - The ACCC #6 and the balcony plates have been lowered by approximately 200 mm to increase the clearance during transport of the calorimeter. - The DNB HV line has been re-routed to avoid a clash during transport of coils ACCC #4 and #5. - The horizontal ceiling beams at the rear area of the NB cell have been modified to allow monorail continuity between the DNB branch and the branch to the storage area. A full clearance analysis has been made with the final monorail layout and crane design. Allowing 1335 mm for the monorail + crane + interface assembly and 40 mm for manufacturing and assembly tolerances, the maximum vertical clearance with the optimized crane is 3205 mm. The main results concerning the extraction of the components may be summarized like this: - The BLC’s symmetry axes are aligned with the crane and their mass is below the crane payload.
Fig. 7. Detail of the transportation of on ACCC coil.
- The ACCC’s and PS plates have their CoG aligned with the crane vertical axis. - The front components are extracted from the toroidal branch of the rail system. They are in general off-centered with respect to the crane. The heaviest components are the balcony plates (30 tonnes) that can be 0.5 m off-centered. The absolute valve is also a heavy component with an estimated weight of 20 tonnes and 0.6 m of CoG misalignment. But with only one exception, all the Front components can be extracted with crane, with safety margins ranging from 16% to 88%. The exception corresponds to the fast shutter of the HNB #3. Its large CoG misalignment (1352 mm) puts its CoG out of the crane footprint. A special frame will be needed to extract this component, that is otherwise not heavy (2 tonnes). Concerning the displacement of the components the following results can be stated: - The BLC’s can be transported as extracted, with no tilt angle. - The ACCC’s must be tilted with respect to the rail axis by as much as 48◦ in order to reduce their horizontal footprint. A CAD view of the coil during transport can be seen in Fig. 7. - The PS plates must be tilted with respect to the rail axis by 32◦ in order to reduce their horizontal footprint. - The front components can be transported as extracted, no inclination is needed A study of the maximum dimensions of components compatible with the current design of the rail and crane system has been carried out, the results are summarized in Table 2. 5. Summary A design for an overhead crane in the neutral beam cell of ITER is presented. The crane will be used to perform the maintenance of the beam line components and front components of the three H&CD NB’s and the diagnostic NB by remote handling, using a top access approach.
Table 2 Maximum dimension of components transportable with the crane. Length Width Height Inclination (X axis)
7.60 0.10 2.80 0
6.00 1.70 2.80 0
5.00 2.40 2.80 0
4.00 2.90 2.80 0
3.00 3.30 2.80 0
2.00 3.50 2.80 0
6.00 2.40 1.60 30◦
5.00 3.10 1.20 30◦
4.00 3.60 0.90 30◦
3.00 4.00 0.70 30◦
2.00 4.20 0.60 30◦
6.00 2.80 0.85 45◦
5.00 3.50 0.20 45◦
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The crane system consists of a monorail, a carriage and a lifting mechanism. A monorail layout has been found that allows access to all the components and a temporary storage area at the rear of the NB cell. Translational rail switches are proposed to perform the necessary rail changes at the intersection between radial and toroidal branches. The carriage has been designed with large transverse dimensions in order to handle heavy, off-centered loads with good stability. Two sub-carriages will lend the system the necessary radius of curvature. The lifting mechanism proposed is electromechanical, with four independent drums and a payload of 50 tonnes. A comparison with a hydraulic system and an electromechanical crane of lower payload is presented. A space availability study has been performed, that has thrown light on a number of mechanical interferences. Correcting actions have been taken whenever possible.
Acknowledgement The reported work has been carried out by CIEMAT/IBERTEF under EFDA contract FU06-CT-2006-00142 (EFDA/06-1456). References [1] E. Polunovskiy, H. Iida, Review of past and recent analysis for the NBI system, EFDA report EFDA D 2599YE (2007). [2] RFX NBTF TN 008 Final report of the EFDA Task: TW4-THHN-IITF2—the first ITER NB Injector and the ITER. [3] ITER Design Description Document N53 DDD 29 01-07-03 R0.1 Neutral Beam Heating and Current Drive (NB H & CD) System (DDD 5.3), IAEA (2003). [4] CATIA model: RH-Assembly DET-00038n39.CATProduct, March 9, 2007.
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Design of an overhead crane for the ITER NB cell remote handling maintenance operations Gonzalo Taubmann a , Laurent Brochet a , Macarena Liniers b,∗ , Mercedes Medrano b , Xabier Sarasola b , Jose Botija b , Javier Alonso b , Carlo Damiani c a b c
IBERTEF A.I.E., Ibérica de Tecnología de Fusión, C/Magallanes 3, 28015 Madrid, Spain Asociación EURATOM-CIEMAT para la Fusión, Av. Complutense 22, 28040 Madrid, Spain FUSION FOR ENERGY, Josep Pla 2, Torres Diagonal Litoral Ed B3, 08019 Barcelona, Spain
a r t i c l e
i n f o
Article history: Available online 17 January 2009 Keywords: Neutral beam heating ITER Neutral beam cell Remote handling Monorail crane
a b s t r a c t In the neutral beam cell of ITER all the maintenance operations on the neutral beam components (BLC’s) must be performed by an overhead crane of large payload capability (30–50 tonnes). A crane system is presented consisting of a monorail, a carriage, and a lifting mechanism. The monorail must give access to the BLC’s in the beam line vessel, the front components connecting the NB vessel with the Tokamak, and a storage area at the north end of the NB cell. Rail switching points are required at the intersections between radial and toroidal branches. A translational switching mechanism is proposed. The crane carriage consists of two independent sub-carriages, each composed of four wheels. A set of four secondary wheels attached to the main carriage prevents the crane tilting due to the CoG misalignment of some loads. The elevation system proposed consists of an electromechanical crane of four independent drums and 50 tonnes payload. In parallel with the crane design, a logistics and space availability study has been carried out, leading to the detection of clearance or transport problems that could be taken into account in the final crane design. © 2008 Elsevier B.V. All rights reserved.
1. Introduction The neutral beam cell of ITER will house the three heating and current drive neutral beamlines (H&CD NB), and the diagnostic neutral beam (DNB). The estimated radiation level in the NB cell after 1000 h of Tokamak operation is enough to preclude manned interventions exceeding 30 min duration (Ref. [1]). Therefore provision is being made so that all the maintenance operations inside the NB cell can be performed by remote handling means. Logistics and space availability arguments have led to adopt the top maintenance scenario for the beam line components (BLC’s) and front components (FC’s) of the neutral beams (Ref. [2]), therefore the operations involved in the removal and reinstallation of any component shall be performed to a large extent by means of an overhead crane. The removed components will be transported with the crane to the hot cell entrance, in the east wall of the NB cell. The structural layout of the NB cell dictates the use of a monorail system: at the Tokamak side, the bioshield and front columns limit the horizontal clearance, whereas the available space above the beam line vessel is restricted by the NB cell pillars and the ion source bushing. Fig. 1 shows a schematic representation of the NB
∗ Corresponding author. Tel.: +34 91 346 0844; fax: +34 91 346 6124. E-mail address: [email protected] (M. Liniers). 0920-3796/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2008.11.058
cell with the monorail layout: the four radial branches on top of each injector will be used for the BLC’s maintenance, the toroidal branch has been laid down to optimize the service to the front components and the Tokamak upper port plugs. At the back of the injectors, along the NB cell north wall a temporary storage area has been foreseen, to accommodate some large size components that need to be removed in order to access the NB vessel top lid. Among those components are the top coils #4 and #5, and the passive shield plates, both belonging to the magnetic field reduction system (MFRS) (Ref. [3]). Rail switches are needed to connect the radial and toroidal branches during transport. A translational mechanism is proposed, after some detailed analysis of two alternative options. The advantages of the chosen mechanism are discussed in Section 2. The final layout of the monorail system is a result of the space availability study performed using the CAD models of the neutral beam cell and the present design of the BLC and FC components (Ref. [4]). In the final analysis the crane design has been included. The limits to the components dimensions set by the transport process have been established in this way, as well as the main crane requirements, such as payload and load maneuverability. The crane and rail have been designed for a payload of 50 tonnes. Although the weight of the components to be handled is under 30 tonnes, the crane must be dimensioned to manage large off center loads to ensure maneuverability of components at the front side, where
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Fig. 2. Front view of the rail and carriage. The auxiliary wheels are also shown.
Fig. 1. Top view of the NB cell from a CAD 3D model. The three H&CD injectors and the DNB injector are shown. The area near the north wall is used as temporary storage area.
a single toroidal rail must reach the NB front components and the upper port plugs. A further reason to adopt a high-payload crane is to leave open the possibility of transporting some heavy equipment needed for the ion source maintenance at the back area of the cell. The “maintenance corridors” defined by the removal and transport of all the components shall be respected, the laydown of the auxiliary systems such as cable trays, water cooling and cryolines, will be designed in accordance with this condition. Section 4 summarizes the main results of the space availability analysis. The crane itself has been the object of a thorough study. The carriage and elevation system are described in Section 3. Two different elevation systems have been put forward: an electromechanical system and a hydraulic one. The chosen option is the electromechanical crane, the hydraulic option has been discarded on safety grounds, the use of pressurized water in the NB cell is avoided to minimize the risk of water leaks. 2. The monorail and rail switches The crane has been designed for a payload of 50 tonnes if the CoG of the load is aligned with the crane vertical axis. A large payload of 50 tonnes is best managed by using a 4-rope lifting mechanism, which ensures load stability in the case of off-centred loads. If the CoG is not inside the crane “footprint” the extraction would produce a fast rotation and lateral displacement of the load right after the component is disengaged. As this is not acceptable, the layout of the rails and the lateral dimensions of the crane have been designed so that the centres of gravity of all the components are below the footprint of the crane at the moment of extraction. Fig. 2 shows a front view of the rail and a crane with a 2 m distance between ropes. The rail has similar shape than a standard HEB 500 profile, except that the lower wing is 60 mm (instead of 28 mm in the HEB 500) to avoid local bending. The deflection of the rail has been calculated as a function of the distance between supports to the ceiling. In the conservative assumption of a concentrated load, the deflection is below 1 mm for distances between supports up to 3 m. The width of the rail is 300 mm (±150 mm) so the maximum possible distance between wheels in transverse direction is approximately 260 mm. If the CoG of the equipment is misaligned with the rail vertical axis by more than 130 mm, the crane will rotate and the
equipment will have a lateral movement. To avoid this effect two lateral sets of reaction wheels are provided at each side of the crane. In case of off-centred loads, the crane will try to rotate and a reaction force is developed on the stability wheels. In this scenario, the load developed on the main wheels is larger than the weight of the equipment. If a shift between the load CoG and the crane axis exists, the load capability of the crane is diminished. For a given payload, the lateral dimensions of the crane define the maximum weight that can be extracted as a function of the misalignment between the CoG of the load and the rail vertical axis. In Fig. 3 there are plots of the maximum weight and the loads on the main and secondary wheels for a payload of 50 tonnes and a distance between ropes of 2 m. At the intersections between the radial and toroidal branches of the monorail, rail-switching devices are needed. Three different alternatives have been examined: the rotational switch, the translational switch and the toroidal rail. They are schematically represented in Fig. 4. Fig. 4a shows a layout of the rotational switch option. In order to cover all the required areas four switches are needed. During operation of the switching mechanism, the crane carriage hangs from the device, the rotating mechanism must cope with the full load of the crane. When the carriage is inside the rail-switch, a mechanical hard stop must be activated to ensure that the carriage will not move. A further difficulty of this kind of device is that a curtain type umbilical cannot be used. Therefore, friction contacts must be used for electric power and signals. For hydraulics, local connections could be used if required. The mechanical motion is achieved by rotating an external crown with respect to an internal, fixed crown. The movement is driven by an electric motor located in the upper level, engaged to the bearing crown through a pinion.
Fig. 3. Plot of the maximum load and loads on the main and secondary wheels as a function of CoG misalignment.
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upper level and connected to the device trough a rack and pinion. The translational switches are compatible with the use of a curtain type umbilical. Fig. 4c shows the general layout of the rail system in the NB cell when a toroidal rail is used near the Tokamak. The toroidal concept requires two carriages: the crane carriage, similar to that used in the previous options, and the toroidal mover carriage that performs the toroidal movement carrying the crane carriage along. The toroidal mover carriage has the ability to move toroidally and stop right in front of a radial rail. In this position, the crane carriage can move along the radial rail. The toroidal mover carriage has the maximum length allowed by the columns of the building. The area covered by the crane is increased significantly as compared with the other switching systems. The toroidal movement requires wheels to displace and support the carriage from the toroidal fixed rails. Four lines of wheels will perform this duty. The motorization of the toroidal movement is installed over the toroidal mover carriage and will consist of a pinion-rack system. Two racks are fixed on the ceiling at both sides of the toroidal mover carriage, and two independent drivers composed of a DC motor, a gearbox and a pinion will be fixed on the carriage and engage with the ceiling racks. The toroidal mover system allows the use of a curtain type umbilical. Of the three switching systems, the translational switch is recommended for its reliability and simplicity. The main advantages are that the rail switch operations are performed under no load conditions, and that it requires a minimum number of switch manoeuvres for a given maintenance action, thereby reducing the risk of failure. 3. The crane: carriage and lifting mechanism
Fig. 4. Layout of the monorail with (a) rotational rail switches, (b) translational rail switches, (c) toroidal rail system.
Fig. 4b displays the monorail layout with translational rail switches. As in the rotational case, four switches are needed to cover the maintenance corridors in the NB cell. The translational switch is conceptually similar to the typical train rail-switch: a sector of rail coincident with the intersection between two directions is substituted with a mobile sector containing the two rails corresponding to both directions. The distance between rails is enough to allow the movement of the carriage without interference with the inactivated rail. The movement of the rail-switch, as opposed to the rotating device, is performed before the carriage hangs from the device, therefore under no load from the crane. Once the rail change is made the carriage can travel across the device, and no further operation of the switch is necessary for the return trip of the crane. Therefore, a given maintenance operation will require a lesser number of switch operations. The displacement of the switch is achieved by means of auxiliary transversal rails fixed to the ceiling. The mobile rails are supported from the transversal rails, therefore their height must be decreased. The loss in stiffness can be compensated using a more robust profile. The driving system consists of a motor located in the
The crane carriage moves along the rail and supports the elevation drivers. The crane dimensions brought over by stability criteria are so large that a monolithic carriage would result in a very large curvature radius. To minimize the curvature radius a solution with two small independent sub-carriages has been selected. As seen in Fig. 5a each sub-carriage is composed of four wheels, a U-shape structure and a free rotation rod to hold the elevation structure. The rod is supported through an axial effect bearing (SKF AXK 130170). Fig. 5b shows the complete carriage assembly with the two subcarriages and the elevation structure attached. Also in the figure are the four stability wheels needed to balance the torque exerted by an off-centre load. The stability wheels are directly attached to the main structure and run on two auxiliary rails parallel to the main rail. In the design of the elevation system the following criteria have been taken into account: - Vertical size. In the NB cell the vertical clearance between the ceiling and the highest material point along the crane way is 4580 mm. Within this distance must be accomodated the complete crane (rail + carriage + elevation system + grabbing frame) and the NB component to be handled, whose height can be as large as 2800 mm (calorimeter). Therefore, there is strong interest in making the vertical dimension of the crane as small as possible. - Number of ropes. The elevation system needs to handle large loads with great accuracy and stability. A 4-rope solution has therefore been chosen. - Independent movement of the ropes. It allows rotation of the load around two axes: the rail axis, and a transverse horizontal axis. This operational flexibility is needed to increase the transportability of large components by reducing their footprint, and to attain the required accuracy at component installation. Moreover the size of the gears or pistons is reduced with four independent ropes, thereby gaining in vertical clearance.
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Table 1 Comparison between electromechanical and hydraulic cranes. Construction case
Units
Commer.
Electromechanical
Maximum load Equipment rotation Height Length Width
tonne
25.4 X and Y 1444 3626 1500
30 X 1309 1800 2000
mm mm mm
Hydraulic
X and Y 1261 1800 2000
50 X 1459 3100 2060
X and Y 1285 3450 2060
30 X and Y 1239 4180 2428
50 X and Y 1319 4180 2428
Height represents the vertical distance between the roof and the lower level of the frame.
- Load capacity per rope. Ropes will have to withstand different loads depending on the position of the CoG. In the limit, if the CoG is precisely under a rope this rope will withstand the full load and the others will have no load. - Rope position control. Each rope has an independent position sensor to measure the vertical position of the frame. This system is independent of the elongation of the rope, so differential deformation can be compensated by the elevation system. Three different elevation systems have been studied, all of them fulfilling these criteria: 1. A commercial 30 tonnes).
electromechanical
crane
(maximum
load
Fig. 5. (a) Drawing of one of the two sub-carriages. (b) The two sub-carriages, the stability wheels and elevation system structure.
2. A four piston hydraulic crane (30 or 50 tonnes). 3. A custom made electromechanical crane (30 or 50 tonnes). Only the third crane will be described here, the comparison between the three options is summarized in Table 1. Fig. 6 presents a view of a CAD model of the 50 tonnes electromechanical crane. There are four drivers each composed of an electric motor and two gears. Each driver acts on a drum that elevates one rope. A parallel architecture drum-motor has been chosen in order to reduce the length of the crane. The reliability of the system is increased by including two redundant motors for each drum. An axial displacement will be provided to the drums so the rope keeps a constant position during elevation of the component. In the figure is shown the grappling frame with the latches that will grab and hold the component. Not shown are the security latches that attach the frame to the carriage so that transportation of the component is carried out in a safe way. Table 1 summarizes the dimensional and operational properties of the three cranes. The commercial version is only available for a maximum load of 30 tonnes therefore it must be ruled out if a payload of 50 tonnes is required. But it is shown here as a reference. The operational capabilities (rotation around X and Y axes) and the position accuracy of the electromechanical and hydraulic cranes are the same, the vertical dimension is similar in both cases, while the transverse dimensions of the hydraulic crane are larger. As shown in the table, four independent ropes (X and Y rotation) are advantageous over two sets of ropes on account of the vertical dimension, since the size of the gears/pistons is reduced. The payload choice has also an influence on the vertical dimension, but the gain achieved by reducing the payload from 50 to 30 tonnes (20 mm for the electromechanical or 80 mm for the hydraulic crane) does not justify the loss of manoeuvrability of large, off-centre loads. The hydraulic system requires an umbilical and the use of high-pressure (25 MPa) water tubes. This has been considered a drawback of the hydraulic option since there is a risk of a water leak in the NB cell. Taking into account all these considerations, the electromechanical crane of 50 tonnes and four independent ropes is the preferred option.
Fig. 6. View of the electromechanical crane with the grabbing frame.
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4. Space availability The space availability study concerns the neutral beam components whose maintenance is to be performed by the crane, and those that need to be removed in order to get access to them. These components are listed below: - Inside the NB vessel. Neutralizer, ion dump and calorimeter. - To get access to the NB vessel top lid, the following components must be removed. Active compensation coils (ACCC’s) #4 and #5, the passive shield (PS) plates. - The front components (FC’s). Shutter, absolute valve and duct bellows. - To get access to the FC’s. The balcony plates. The operations to be performed by the crane are essentially the removal of the component, its transport to the hot cell door, and the reverse operations of transport from the hot cell door and reinstallation of the component. Transport of the ACCC’s and PS plates to the temporary storage area must also be analysed. The main constraints to the space availability are: - The NB cell structure: the ceiling, horizontal beams, columns. - The layout of the H&CD NB’s and DNB, in particular the NB source bushings. - The layout of the vacuum vessel pressure suppression system (VVPSS). - The monorail layout and the crane. The space availability study depends on the monorail layout and the crane design that were proceeding in parallel. Therefore the study has advanced in an iterative way: starting with a monorail layout and preliminary crane design, the problems encountered were taken as input for a new design. Whenever the encountered clash could not be solved with a proper crane design, a proposal was made to modify the component or structural element of the NB cell. Some of the modifications to the NB cell that have resulted from this study are: - The ACCC #6 and the balcony plates have been lowered by approximately 200 mm to increase the clearance during transport of the calorimeter. - The DNB HV line has been re-routed to avoid a clash during transport of coils ACCC #4 and #5. - The horizontal ceiling beams at the rear area of the NB cell have been modified to allow monorail continuity between the DNB branch and the branch to the storage area. A full clearance analysis has been made with the final monorail layout and crane design. Allowing 1335 mm for the monorail + crane + interface assembly and 40 mm for manufacturing and assembly tolerances, the maximum vertical clearance with the optimized crane is 3205 mm. The main results concerning the extraction of the components may be summarized like this: - The BLC’s symmetry axes are aligned with the crane and their mass is below the crane payload.
Fig. 7. Detail of the transportation of on ACCC coil.
- The ACCC’s and PS plates have their CoG aligned with the crane vertical axis. - The front components are extracted from the toroidal branch of the rail system. They are in general off-centered with respect to the crane. The heaviest components are the balcony plates (30 tonnes) that can be 0.5 m off-centered. The absolute valve is also a heavy component with an estimated weight of 20 tonnes and 0.6 m of CoG misalignment. But with only one exception, all the Front components can be extracted with crane, with safety margins ranging from 16% to 88%. The exception corresponds to the fast shutter of the HNB #3. Its large CoG misalignment (1352 mm) puts its CoG out of the crane footprint. A special frame will be needed to extract this component, that is otherwise not heavy (2 tonnes). Concerning the displacement of the components the following results can be stated: - The BLC’s can be transported as extracted, with no tilt angle. - The ACCC’s must be tilted with respect to the rail axis by as much as 48◦ in order to reduce their horizontal footprint. A CAD view of the coil during transport can be seen in Fig. 7. - The PS plates must be tilted with respect to the rail axis by 32◦ in order to reduce their horizontal footprint. - The front components can be transported as extracted, no inclination is needed A study of the maximum dimensions of components compatible with the current design of the rail and crane system has been carried out, the results are summarized in Table 2. 5. Summary A design for an overhead crane in the neutral beam cell of ITER is presented. The crane will be used to perform the maintenance of the beam line components and front components of the three H&CD NB’s and the diagnostic NB by remote handling, using a top access approach.
Table 2 Maximum dimension of components transportable with the crane. Length Width Height Inclination (X axis)
7.60 0.10 2.80 0
6.00 1.70 2.80 0
5.00 2.40 2.80 0
4.00 2.90 2.80 0
3.00 3.30 2.80 0
2.00 3.50 2.80 0
6.00 2.40 1.60 30◦
5.00 3.10 1.20 30◦
4.00 3.60 0.90 30◦
3.00 4.00 0.70 30◦
2.00 4.20 0.60 30◦
6.00 2.80 0.85 45◦
5.00 3.50 0.20 45◦
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The crane system consists of a monorail, a carriage and a lifting mechanism. A monorail layout has been found that allows access to all the components and a temporary storage area at the rear of the NB cell. Translational rail switches are proposed to perform the necessary rail changes at the intersection between radial and toroidal branches. The carriage has been designed with large transverse dimensions in order to handle heavy, off-centered loads with good stability. Two sub-carriages will lend the system the necessary radius of curvature. The lifting mechanism proposed is electromechanical, with four independent drums and a payload of 50 tonnes. A comparison with a hydraulic system and an electromechanical crane of lower payload is presented. A space availability study has been performed, that has thrown light on a number of mechanical interferences. Correcting actions have been taken whenever possible.
Acknowledgement The reported work has been carried out by CIEMAT/IBERTEF under EFDA contract FU06-CT-2006-00142 (EFDA/06-1456). References [1] E. Polunovskiy, H. Iida, Review of past and recent analysis for the NBI system, EFDA report EFDA D 2599YE (2007). [2] RFX NBTF TN 008 Final report of the EFDA Task: TW4-THHN-IITF2—the first ITER NB Injector and the ITER. [3] ITER Design Description Document N53 DDD 29 01-07-03 R0.1 Neutral Beam Heating and Current Drive (NB H & CD) System (DDD 5.3), IAEA (2003). [4] CATIA model: RH-Assembly DET-00038n39.CATProduct, March 9, 2007.